Time is wasting for President Obama and Congress to approve a bill pumping $500 billion into America's transportation network, Rep. Tim Walz, DFL-Minn., said this week.

The transportation proposal has drawn a lukewarm response from Obama, who wants to postpone considering it for 18 months to let Congress focus on health care, climate change and the financial markets.

The bill would overhaul the bureaucracy guiding federal transportation policy while pouring $450 billion into America's roads and bridges over the next six years - $124 billion more than what's called for under the current federal blueprint.

The measure also includes a landmark $50 billion investment in a high-speed rail network that could include a Chicago-to-St. Paul line, possibly through Winona.

The bill is sponsored by Rep. Jim Oberstar, DFL-Minn., who says his proposal would create millions of jobs and aid businesses hampered by traffic bottlenecks and other flaws in the nation's current transportation network.

But it's hampered by a big question: How to pay for it?

Oberstar has suggested increasing the federal gas tax or implementing a mileage tax, and Walz said Thursday that a tax on oil speculators also is on the table. Walz acknowledged a tax hike may not be popular, but he said there's also a cost to letting America's infrastructure crumble. That point is acknowledged by the U.S. Chamber of Commerce, which is pushing for more investment in highways.

Walz also seemed to criticize Obama's lack of enthusiasm to tackle the transportation issue.

"We need to figure out: What's a fair way to do this?" Walz said. "It shows limited leadership to make blanket statements and take anything off the table."

In allying with Oberstar, Walz is taking sides with one of America's most powerful lawmakers in the arena of transportation funding. Oberstar is chairman of the U.S. House Transportation and Infrastructure Committee. Walz sits on the committee.

Oberstar has clashed with the Obama administration on the bill, even vowing to "roll over" the White House if it won't cooperate. But an Oberstar spokesman acknowledged last month that the bill is unlikely to be considered this fall. As a stopgap, the House voted last week to extend the current transportation-funding framework for at least three months.